According to the present state of the art, a number of products containing plastics for use in the medical field are commercially available. In many of these products, an essential component is a tube with one or several lumen/lumina. These products are sterilized, e.g. with ethylene oxide, and commercially available in air-tight packaging.
Once taken out of the packaging, however, they are no longer sterile. Impermeable and smooth materials are preferably used for such products in order to minimize the colonisation by bacteria and fungi. However, particularly when used for a longer period of time or even for long-term application, these products can be subject to a colonisation by germs, which finally do harm to the patient using these products.
Scientists trying to add small amounts of antibiotics, also in combination with metal-containing compounds, or to apply antibiotics-containing coatings to products of the above-described type have obviously not been successful, at least up to now, e.g. U.S. Pat. No. 4,612,337. The main risk in this context is the development of resistance to antibiotics due to the long-term release of low amounts of antibiotics.
The anti-microbial properties of silver are also of importance. Even traces of silver and its salts have bacteriostatic and bactericidal effects. This disinfecting effect is caused by the "oligodynamy" phenomenon found by C. von Naegli in 1893, which is supposedly based on the dissolving silver ions.
Also the "Composition for decontaminating liquids containing germs" disclosed in German patent DE-900 000 works on to this principle. The composition contains a complex salt consisting of a heavy metal salt with specific oligodynamic effect (e.g. Ag) and a soluble halide capable of forming a complex salt, a readily soluble salt of a metal or an organic base.
DE-A-37 25 728, EP-A-0 301 717 and U.S. Pat. No. 4,054,139 disclose medical polymer materials, in which silver (compounds) is/are mechanically introduced into the material. A sufficiently long-lasting sterility cannot be achieved with these materials, either. Nor did trying to treat such products with a strongly bactericidal silver nitrate in order to obtain sterility for a long period of time lead to positive results. Due to its solubility in water, the silver nitrate was probably simply washed out.
The bactericidal and/or fungicidal effects of other metals are also well known. For instance those of copper, which is described in EP-A-0 116 865 and which particularly exhibits also a strong fungicidal effect, as well as those of gold, zinc and cerium, which are also disclosed in U.S. Pat. No. 4,612,337.
However, so far researchers have not succeeded in obtaining satisfying results in impregnating plastics parts with these metals.
Besides, the bactericidal and/or fungicidal effects of these metals are not sufficient to satisfy all practical requirements. On the contrary, there is a need for means based on such metals in which, however, the bactericidal and/or fungicidal effect of these metals is increased.